Method for controlling an electric machine and control device

ABSTRACT

A method for controlling an electric machine or electric unit by actuating a component of the electric machine or unit using a predicate and by automatically examining the component in regard to the performance of the predicate to permit examination of an automated system for possible errors in a simply manner, wherein the predicate contains an expected value of a (physical) quantity of the component, and wherein in the examination of the component, a check is performed to determine whether the expected value actually arises when the predicate is performed such that erroneous situations can be detected by a runtime system without explicit programming being necessary therefor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a U.S. national stage of application No. PCT/EP2010/003880 filed24 Jun. 2010.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for controlling an electricmachine or unit by actuating a component of the electric machine or unitusing a predicate and by examining the component in regard to theperformance of the predicate.

2. Description of the Related Art

In control technology, the predicate is understood to be the functionalrelationship between several components (generally, subject and object).A drive is switched on using a switch for instance. The switch is thesubject here, the drive is the object and the switch-on process is thepredicate.

Automation-specific solutions are currently created in most instances byexplicit programming of the object to be achieved. The programming ofthe solution does not, however, constitute the main part of theprogramming outlay. The tests which are to result in them reactingaccordingly in the event of an error and if necessary generating acorresponding error message are even more complicated than the actualsolution.

WO 2006/084666 A1 describes a system for checking and evaluatingoperation-dependent processes and/or components, which includes a robot,which records measured values using at least one sensor on an operatingand/or control element of the components to be checked or evaluated. Ina central evaluation unit, the measured values are analyzed andevaluated with the aid of defined quality functions.

DE 100 17 708 A1 describes a method for controlling mechanisms ortechnical systems in which the mechanisms or technical systems to becontrolled are stored in a controller, in terms of their elementaryfunctions, with their states defined according to command and theassociated signal images of the sensors and actuators. Based on adefined reference state at the start of the control activation, acontinuous comparison of the actual states notified by the technicalunit by the sensors occurs with the target state stored in thecontroller for all elementary functions.

WO 2008/090432 A1 discloses an electric device, i.e., a householdappliance. For self-diagnosis of the household appliance, the electricalquantities of the components are fed to a control facility when theelectrical components are switched on, where the control facilitycompares these quantities that are stored in a storage facility.

System states and error possibilities have previously been examinedexplicitly and therefore form part of the automation-specificprogramming. However, this is disadvantageous in that, on the one hand,the possibility of an error must be identified as such. This servicemust be provided by the programmer. On the other hand, it is complicatedto test these program parts, because the error state has to be simulatedor produced to do so.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a methodfor identifying errors in automation solutions with less effort.

This and other objects and advantages are achieved in accordance withthe invention by a method for controlling an electric machine orelectric unit by actuating a component of the electric machine orelectric unit using a predicate in which a functional relationship isdefined between a subject and the component, where the predicatecontains an expected value of a quantity of the component, and byautomatically examining the component in regard to the performance ofthe predicate and where in the examination of the component, a check isperformed to determine whether the expected value actually occurs whenthe predicate is performed, where the component includes aself-description, which contains run-time information that is used inthe examination as reference for the quantity, and where a controlsignal for the electric machine or electric unit is obtained from thedifference between the reference for the quantity and the value to beexpected.

It is also an object of the invention to provide a control device for anelectric machine or electric unit having an actuating facility foractuating a component of the electric machine or electric unit using apredicate in which a functional relationship is defined between asubject and the component, where the predicate contains a value to beexpected of a quantity of the component and an examination facility forautomatically examining the component in regard to the performance of apredicate, where the examination facility can check whether the expectedvalue actually occurs when the predicate is performed, where thecomponent in a run-time system includes a self-description, whichcontains run-time information, and where the run-time system isconfigured to obtain a control signal for the electric machine orelectric unit from a difference between the reference for the quantityand the value to be expected.

The term “quantity” is understood here to mean, for instance, a physicalor calculated quantity. Its value can be absolute or relative, but mayalso be non-specific (e.g., increase).

The predicate, in other words the function, which has to be performed,is advantageously combined with an expectation (i.e., a value to beexpected). This therefore already implicitly specifies whichconsequences the performance of the predicate has. If these consequencesdo not arise, an error appears in the system and it can respondaccordingly. Conversely, if the consequences arise, the system operatesin an error-free manner.

In the examination, the (physical) quantity of the component ispreferably measured, and the resulting measured value is correspondinglyexamined to determine whether it falls within an estimated range, whichis based on the value to be expected and which can be stored as run-timeinformation relating to the component. An actual measurement istherefore implemented, and the obtained measured value is compared withthe value to be expected from the predicate or a value that results fromthe value to be expected, such as by the offset. The comparison resultcan be used for control or information purposes.

In a specific embodiment, the value to be expected may be a relativevalue. The predicate is therefore not restricted thereto, such that onlyabsolute “expected values” can be transmitted therewith, but insteadrelative values, such as an increase or decrease, can be linked to thepredicate. A specific increase would be “+3 A”, for instance, anon-specific increase would be “increase”.

Furthermore, an error message can automatically be generated if theexpected value does not actually arise when the predicate is performed.This is advantageous insofar as some errors can be immediately displayedto draw conclusions as quickly as possible.

In a specific exemplary embodiment, the component may be a drive. Thecomponent may, however, also be any other unit in an automated system,e.g. bulb, relay or any other actuator.

Furthermore, run-time information can be specified for the component,which is used as a reference for the (physical) quantity in theexamination. This run-time information is a physical quantity, such asthe speed or the power consumption, such during the run time of theelectric machine or unit. If this run-time information is stored in acontrol program pertaining to the component, the system can be examinedusing the control program.

The predicate may mean that the component is switched on or off. It may,however, also mean another function, e.g., “implementing a step” in astepper motor or another function of an automated system.

Furthermore, the (physical) quantity, for which an expected value iscontained in the predicate, may be the current, the voltage or thespeed. This may essentially be a (physical) quantity or also any otherquantity which can be measured for examination on the component (e.g.,frequency, brightness or CO₂ discharge).

Other objects and features of the present invention will become apparentfrom the following detailed description considered in conjunction withthe accompanying drawings. It is to be understood, however, that thedrawings are designed solely for purposes of illustration and not as adefinition of the limits of the invention, for which reference should bemade to the appended claims. It should be further understood that thedrawings are not necessarily drawn to scale and that, unless otherwiseindicated, they are merely intended to conceptually illustrate thestructures and procedures described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is now explained in more detail with the aid ofthe appended drawing, in which:

FIG. 1 shows a schematic block diagram of the method or the controldevice in accordance with the invention; and

FIG. 2 is a flowchart of the method in accordance with the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The exemplary embodiments shown in more detail below represent preferredembodiments of the present invention.

The programming of an automation-specific unit by functional modelingand the semantic description of the functional relationships inventivelyoffers new possibilities of automatically detecting error situations.The basic idea consists in expanding the description of functionalrelationships by non-functional aspects. The additional information thatrelates to these non-functional aspects is used at generation time(e.g., in the engineering system) and at run time (in a run-timesystem), in order to automatically address obligatory boundaryconditions and error situations.

The automatic examination relieves the application creator (projectengineer) of routine tasks. Furthermore, a frequent source of error inunit development is minimized, because in an average unit developmentaccording to the current standard, an application creator typicallyspends 30% of his/her development time in creating component tests orsimilar tasks for treating errors. Attempts are therefore made toidentify error situations by the run-time system, without explicitprogramming being required therefor. Furthermore, automatic generationof human-readable error messages would also be advantageous.

A particular embodiment is shown in more detail below in the example ofFIG. 1. The controller of an individual component 1, which representsthe object, is considered here by way of example from an overall system.The object or the component 1 is a drive for instance. The drive isactuated by a switch that represents the subject 2. The functionalrelationship between the subject 2 and the object or the component 1 isdefined in the predicate 3. Here, the predicate 3 represents thefunction “switch on”. The predicate 3 links subject 2 and object(component) 1 by means of the corresponding function. In the presentexample, the functional relationship reads: “The drive is switched on bya switch”. Each relationship between the components of an automatedsystem can in general be represented by a similar functional link.

The components in a run-time system (e.g., sensors, drives orsubsystems) have a strictly typed functional interface. This means thata component can only be actuated with rigidly predetermined commands(e.g., switch-on, switch-off). The components 1 in the run-time systemcan also have a self-description 4. These may be typed,product-describing properties, such as data for a drive. Such data 41,42 would be, for instance, the current consumption I=2 . . . 5 A and thespeed n=0 . . . 500 rpm. Furthermore, the self-description 4 of acomponent 1 may also contain typed run-time information 43. In thepresent example, the run-time information 43 reads for instance: currentconsumption I_ist=2 A. This run-time information is measured as currentinformation and stored in the corresponding data field.

In the example, the figure, in other words the drive, should be switchedon by the switch according to the predicate 3 (“on”). The components(the subject 2 is likewise a component) are connected by functionalrelationships (predicates). In addition to the main function 31 (here“on”=switch on), the predicates also have a semantic description 32relating to the possible effects of the predicate 3 on the components 1,2. In the present example, the current consumption and the speed shouldincrease by the predicate “on” (switch on). The semantic description 32indicates here that an increase in current by 3 A is expected when thedrive is switched on. The semantic information exists in a manner so asto be interpreted by machines.

The connection of components 1, 2 by predicates 3 within the scope ofprogramming implicitly connects information that uses the run-timesystem to implement integration tests (tests prior to commissioning) ortests during operation. In the present example, in accordance withpredicate 3, it is expected that the drive 1 has a current consumptionincreased by 3A after switch-on. The property 42 stored in respect ofdrive 1 indicates that the current consumption of the drive 1 has to liebetween 2 and 4A. When idling, the electric drive therefore has acurrent consumption of 2A by means of the control electronics and acurrent consumption of 5A with a maximum output. The run time such thatthe current consumption is I_ist=2A is now provided to the drive 1. Thismeans that despite the drive being switched on, there has been noincrease in the current consumption. It remains instead at 2A. This inturn means that the actual current consumption does not correspond tothe expected current consumption because the expected value for thecurrent consumption would be 2A (basic current)+3A (relativeincrease)=5A.

The run-time system may, however, also be geared to the change in thecurrent consumption in the actual instance. In the present case, therelative change actually amounts to 0 (ΔI_ist=0), while the expectedchange in current consumption amounts to ΔI=3A. The run-time systemdetermines this difference and generates a corresponding error message5. Alternatively, a control signal can also be obtained from thisinformation for the system, i.e., the unit and/or electric machine. Theerror message and/or information can therefore be generated based on thesemantic description and typed component properties. One example of ahuman-readable error message would be “error during switch-on” or “toolittle current during switch-on”.

In accordance with the disclosed embodiments of the invention, errorsituations can therefore be identified by the run-time system withoutprogramming being explicitly required therefor. Logic for errordetection is therefore contained in the system.

FIG. 2 is a flowchart of a method for controlling an electric machine orelectric unit. The method comprises actuating a component of theelectric machine or electric unit using a predicate in which afunctional relationship is defined between a subject and the component,as indicated in step 210. Here, the predicate including an expectedvalue of a quantity of the component. Next, the component isautomatically examined to determine a performance of the predicate, asindicated in step 220. During examination of the component a check isthen performed to determine whether the expected value occurs when thepredicate is performed, as indicated in step 230.

According to the invention, the component includes a self-descriptionincluding run-time information that is used as a reference for aquantity during the examination, a control signal for the electricmachine or electric unit is obtained from a difference between thereference for the quantity and the expected value.

While there have been shown, described and pointed out fundamental novelfeatures of the invention as applied to a preferred embodiment thereof,it will be understood that various omissions and substitutions andchanges in the form and details of the methods described and the devicesillustrated, and in their operation, may be made by those skilled in theart without departing from the spirit of the invention. For example, itis expressly intended that all combinations of those elements and/ormethod steps which perform substantially the same function insubstantially the same way to achieve the same results are within thescope of the invention. Moreover, it should be recognized thatstructures and/or elements and/or method steps shown and/or described inconnection with any disclosed form or embodiment of the invention may beincorporated in any other disclosed or described or suggested form orembodiment as a general matter of design choice. It is the intention,therefore, to be limited only as indicated by the scope of the claimsappended hereto.

The invention claimed is:
 1. A method for controlling an electricmachine or electric unit, comprising the steps of: actuating a componentof the electric machine or electric unit using a predicate in which afunctional relationship is defined between a subject and the component,the predicate including an expected numerical value of a numericalquantity of the component; automatically examining the component todetermine a performance of the predicate; and checking duringexamination of the component to determine whether the expected numericalvalue is within an estimated range when the predicate is performed, theestimated range being based on the expected numerical value and beingstored as run-time information relating to the component; wherein thecomponent includes a self-description including run-time informationwhich is used as a reference for the numerical quantity during theexamination; and wherein a control signal for the electric machine orelectric unit is obtained from a difference between the reference forthe numerical quantity and the expected numerical value.
 2. The methodas claimed in claim 1, wherein in the examination, the quantity of thecomponent is measured and the resulting measured value is accordinglychecked to determine whether it falls within an estimated range which isbased on the expected numerical value.
 3. The method as claimed in claim2, wherein the expected numerical value is a relative value.
 4. Themethod as claimed in claim 1, wherein the expected numerical value is arelative value.
 5. The method as claimed in claim 1, further comprisingthe step of: generating an error message automatically if the expectednumerical value does not occur when the predicate is performed.
 6. Themethod as claimed in claim 1, wherein the component is a drive.
 7. Themethod as claimed in claim 1, wherein the predicate indicates aswitching on or switching off of the component.
 8. The method as claimedin claim 1, wherein the numerical quantity is one of a current, avoltage or a speed.
 9. A control device for an electric machine orelectronic unit, comprising: an actuation device for actuating acomponent of the electric machine or electric unit using a predicate inwhich a functional relationship is defined between a subject and thecomponent, the predicate including an expected numerical value of anumerical quantity of the component, and an examination facilityconfigured to automatically examine a performance of the component andconfigured to check whether the expected numerical value is within anestimated range when the predicate is performed, the estimated rangebeing based on the expected numerical value and being stored as run-timeinformation relating to the component; wherein the component in arun-time system includes a self-description containing run-timeinformation; and wherein the run-time system is configured to obtain acontrol signal for the electric machine or electric unit from adifference between the reference for the numerical quantity and theexpected numerical value.